This new suction mount is very well made and works great on my Garmin 55. It creates an excellent vacuum and I wouldn't be surprised if it stays mounted should you have an unfortunate crash. My guess is the magnetic mount wouldn't hold your camera in place in the event of a crash. And, the less things flying around like little missiles in the cab of your truck during a crash, the better. This mount also makes it convenient to move my cam to different positions on the windshield or remove it when the weather gets too hot/cold to function correctly.
And, if you're concerned about security you can quickly remove the cam with this mount. In my case I place it in my console which has a built in steel "console vault", which I also highly recommend for peace of mind. Here's a link to the vault: http://www.consolevault.com/console-vault.html